750 splayed port head versus parallel port head - Triumph Forum: Triumph Rat Motorcycle Forums

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post #1 of 9 (permalink) Old 08-04-2010, 06:00 PM Thread Starter
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750 splayed port head versus parallel port head

As I recall the 750 Bonneville went to the parallel port head in 1979, and dropped the splayed port head then for the Bonneville.

Can someone tell me if the '79 thru '81 Bonneville head is essentially the same as the earlier single carb Tiger 750 heads.....and if the Tiger 750 single carb manifold will bolt right up to the '79 and later Bonneville head??

Basically what I'm wanting to do is swap out the tired Bings on my 1981 Bonnie for a simple single carb setup.

thanks,
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post #2 of 9 (permalink) Old 08-04-2010, 07:38 PM
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I wish I could answer you question, but I did try to go with the opposite. I wanted to put a Bonneville manifold and two carbs on my 73 750 Tiger. Never figured it out. The Bonne manifolds were quite a bit different than my Tiger head.

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post #3 of 9 (permalink) Old 08-04-2010, 08:08 PM
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if you want a single carb bike get a TR7 head and associated parts. you will also need to change parts of the airbox assemblys if your bike is using stock airboxes. By your mention of bings I assume your bike is a '81 or later

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post #4 of 9 (permalink) Old 08-04-2010, 08:35 PM Thread Starter
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Yep, my bike is a dual carb Bing, 1981 model year.

What I was hoping is one of these kits would fit the existing parallel port head on the 1981 bike:

http://mapcycle.com/ProductDesc.aspx...-MIKUNI&key=it

fried okra
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post #5 of 9 (permalink) Old 08-04-2010, 11:43 PM
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Well I stopped telling you guys it wont work almost 30 years ago when a guy from florida stopped by the shop(in the chicago burbs) on his way to calif on T100 Triumph with a Horse saddle for a seat.

The ad says for TR7 Head ifin it would fit a T140E head it would say T140E head.
For what is worth it has been my experince the mikuni and amal mk2 carbs are able to use the same intake manifolds. While I'm not an expert on bings bet they use the same manifolds.

If you want to use the kit you showed you WILL NEED A TR7 HEAD.

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post #6 of 9 (permalink) Old 08-05-2010, 05:25 AM
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My 79 parts book (99-7102)
lists TR7 and T140E cylinder blocks as 71-4005 and being common between both bikes.

All I can suggest is to see what your bike's book says and if it's the same part number for the cylinder then a TR7 head should fit.

The twin carb head has steel stubs for a rubber mount tube for each carb, whereas the TR7 carb has a more conventional two stud flange
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post #7 of 9 (permalink) Old 08-05-2010, 08:50 AM Thread Starter
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Thanks, guys....what lead me astray here was the ad referred to TR6 and TR7 models (no reference to the heads) and I harken back to the day when the TR6 was single carb and the TR7 was dual carb bike.

Anyway, single carb 750 heads are pretty rare I gather and my dual carb head has a fairly fresh rebuild.

I guess the primary options I've got are Amal MKll carbs or Mikunis on the existing steel tube stubs. I think "emission carb" when I think of the MKll's.

Any thoughts on the merits of MKll's, versus Mikunis, versus Bings on the parallel dual port heads??

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post #8 of 9 (permalink) Old 08-05-2010, 05:24 PM
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I have the stock Mark II's on my 78 and think they are a decent carb. As far as being an "emission carb" it all depends on how they are jetted and what slide you use. There is a US set of specs and a European set. I don't know much about the Mikunis but my understanding is that they are very similar in design to the Mark II's, so it may come down to cost availablility.

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post #9 of 9 (permalink) Old 08-06-2010, 04:46 AM
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I have Bings on my TSX, Amal mk2s on my TSS and an Amal Mk1 on my TR65 and TR7T.

My comments on each are as follows but note the Mk1 is single and not operating as a pair like the others:

Bing - excellent mpg but needs careful setting up to achieve balancing, tickover, responsiveness etc
Mk2 - not good mpg but less tempremental than the Bing but less responsive
Mk1 - satisfactory mpg - crude, some may say, but consistently effective being less finnicky than then Bing and more responsive than the Mk2 with no flat spots

Bear in mind that the type of bike these are fitted to may effect their assessment. However, 'dem's me views'. Which would I go for ?

Bings- when properly set up, they're wonderful delivering smooth engine performance and,in these hard times, superior economy

Last edited by meriden4ever; 08-06-2010 at 10:14 AM.
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